Various systems exist that purify water using ultraviolet light. In that regard, ultraviolet (UV) light is classified by its wavelength into UV-A, UV-B, and UV-C groups. The first two groups are the relatively-longer wavelength tanning rays emitted by the sun. UV-C (which is also denoted as UVC), however, is a relatively-shorter UV wavelength blocked by atmospheric oxygen and nitrogen to the benefit of life on earth because of its lethal effects. It is these lethal effects that are exploited in UV-C water purification systems to provide potable drinking water.
Potable drinking water is one of the most essential needs for sustaining human life in an emergency or a natural disaster. Portability and light weight are important characteristics for emergency drinking water purification systems, especially for systems which are to meet distributed populations during an emergency. Moreover, portability and light weight are desirable in such systems for serving rural or remote locations. However, conventional UV-C water purification systems are typically inadequate for mobile applications. This inadequacy arises from the need to achieve elimination of substantially all pathogens to achieve potability. For example, even a relatively small volume of water such as an eight ounce drinking glass may contain millions or even billions of pathogens. A 99.9% kill efficiency bacteria or virus inactivation efficiency in a UV-C water purification system could thus pass scores of viable pathogens into the treated water. For pathogens such as cholera bacteria, the results could well be lethal for consumers of the treated water. Thus, governmental agencies such as the United States (US) EPA promulgate very stringent goals for testing pathogen removal—for example, the US EPA requires a removal rate of 99.9999% (6 logs) for bacteria in public drinking water. To attempt to meet such stringent demands, conventional UVC purification systems must ensure that the water being passed through the system receives a sufficient exposure time to the UV-C light. But such systems must also support an adequate flow rate to produce sufficient quantities of water. For example, a typical per capita water consumption is 2 gallons per day such that a system servicing just 1000 people would have to treat at least at least 2000 gallons daily. Thus, conventional UVC water purification systems that meet the stringent US EPA standards are quite heavy so as to provide the necessary flow rate yet also have an adequate dwell time within the system for pathogen elimination. In addition, such conventional UVC water purification systems have substantial power demands and associated costs.
To meet the need for a self-contained purification system that is portable, light weight, and power-efficient, U.S. application Ser. No. 11/862,631 (the '631 application) discloses a UVC water purification system that includes a chamber having baffles defining a plurality of sub-chambers. The baffles are arranged such that each sub-chamber defines a sub-volume or portion of the volume contained by the chamber. For example, in one embodiment, the chamber is an elongated tube subdivided by separate baffles into corresponding sub-chambers. In this fashion, water being purified passes consecutively from sub-chamber to sub-chamber through passageways or conduits defined by the intervening baffles. A UV-C light source illuminates each sub-chamber to eliminate pathogens. The use of baffles to define sub-chambers in this fashion introduces a dramatic increase in the pathogen removal rate as compared to conventional (un-baffled) UV-C water purification systems. For example, if two systems of identical chamber volume, flow rate, and UV-C source power are provided except that one is baffled into sub-chambers as discussed in the '631 application, the baffled system will have a pathogen removal rate that is orders of magnitude greater—for example, a log reduction of 6 in pathogens for the baffled system as compared to a log reduction of below 3 for the un-baffled system.
This dramatic increase in efficiency leads to substantial weight reduction because the un-baffled system in the comparison just discussed would have to be increased in size so that the dwell time within the system is sufficient to produce the desired pathogen removal rate. Alternatively, the un-baffled system would require a substantially greater power UV-C source, which then demands a much heavier generator to provide the necessary power draw by such a larger source. Thus, a relatively small (and thus light weight) baffled system as disclosed in the '631 application can provide the same flow rate of a much heavier conventional UV-C water purification system, yet provide a substantially higher pathogen removal rate.
Regardless of whether baffles are provided or not, the use of an electric pump driven by a generator is typically required by a UV-C water purification system to provide a flow rate sufficient to provide an adequate quantity of treated water in locations in which water utilities providing a sufficient water pressure are unavailable. The weight of the pump and associated generator can be substantial. Accordingly, there is a need in the art for improved UVC water purification systems with light weight pump and generator architectures.